This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Experiments conducted over the past year have demonstrated that analysis of the costimulatory molecule CD28 in conjunction with PD-1 provides a more accurate definition of exhausted T cells;exhausted cells are PD-1-positive and CD28negative, while activated but functional T cells are PD-1-positive and CD28positive. A manuscript describing these findings has been published.